The immobilization of proteins on insoluble surfaces is important in diagnostic instrumentation and in vivo monitoring. Improvements in the surface antibody interactions should result in more efficient approaches to immunodiagnostics. This would be especially useful in the field of tumor marker detection where panels of antigens may be needed for proper diagnosis. The proposed research under Phase II is the development of a multiple immunological test with an electronic endpoint. The research will involve the use of antigen or antibody-labeled colloidal gold particles to generate an electronic endpoint. A diagnostic element will be refined so that the antibody-antigen reaction causes the completion of an open electrical circuit. This model necessitates an electrically insulating base surface for protein adhesion. A pair of conductors is placed on the base defining a channel between them. The antigen is placed in the channel. The gold-tagged antibody will bond to the specific antigen forming a conductive bridge across the channel for a positive reaction. This new type of device could replace the currently used enzyme immunoassay, immunofluorescence and radioimmunoassay techniques which are reliable but are slow, tedious, and restricted to single tests per sample. The commerical applications of a multiple test are broad, encompassing human diagnostics such as cancer and allergy as well as veterinary and forensic diagnostics.